On production of seamless rings on radial-axial ring rolling machines, the ring blanks are usually inserted into the ring rolling machine at a temperature of 900 to 1200° C. and rolled to an outer diameter of preferably 0.2 to 10 m. After rolling, the rings are usually stored intermediately and mostly cooled down to ambient temperature. Within the scope of the subsequent heat treatment it is then required to heat-up the ring again up to a temperature in the austenite range and from there on to cool it down to produce a fine-grained and even fabric. The additional heat treatment involves high expenditure and substantial demand for energy.
Known from EP 413 163 B1 is a method and a device for the production of thermomechanically treated rolling material made of steel, wherein the transformation of the rolling material is carried out in a range of temperature between ambient temperature and a temperature of 930° C., and wherein an accelerated cooling of the rolling material is implemented by the aid of cooling media such as water, air or a mixture of water and air in a cooling facility located downstream in order to improve material properties. This method is provided only for the production of flat and long products as well as rolling wire. The precise way of cooling is not described therein.
Moreover, in the Korean description KR 1005661118 B1, a ring rolling method including a subsequent heating-up of the rolled ring in a kiln and the cooling-down of the ring in a dipping basin are disclosed, wherein the diameter of the rings should range between 4,500 and 9,300 mm while the height is to be within 300 and 280 mm. Here, too, the energy-demanding renewed warming-up of the ring prior to the final immersion cooling is described therein.
The German publication DE 33 14 847 A1 describes a method for the fabrication of seamless rings with improved resilience properties by applying a hot forming process followed by a heat treatment process. Such spring steels must have quite specific properties and are subjected to certain multiple-stage treatments. The procedures are relatively complicated.
Moreover, German publication DE 1 964 795 B discloses a method for the heat treatment of steels immediately from the heat of deformation including an accelerated cooling-down, also implementing a two-stage cooling-down in the way that initially the hot formed material is cooled from a deformation final temperature of 880°-950° with a cooling-down speed of 50°-25° per second down to a temperature which lies 40° 10° above the AI-point, i.e. roughly at 710°-740°. This temperature is then to be maintained for 1 to 20 minutes. Subsequently, the material is cooled down speedily to under the martensite point, i.e. to a temperature of under approx. 320° C.